Despite anecdotal reports of palpitations associated with menopause, there is no medical literature describing the types of arrhythmias which occur or their time-course or response to hormone replacement therapy. The purpose of this study is to test the hypotheses that there is a high prevalence of palpitation during menopause; these correspond to frequent premature atrial and ventricular complexes; these arrhythmias are mediated in part by changes in autonomic control of the heart; and symptoms, arrhythmias and autonomic changes improve after hormone replacement therapy. Women who plan to start hormone replacement therapy will be recruited. Subjects will be asked to fill out a questionnaire about symptoms characteristic of menopause and palpitations and to wear a 24-hour holter monitor twice before and twice after initiating hormone replacement therapy.This study is important because complaints of palpitation are prevalent among perimenopausal women, frequently leading to expensive evaluations. It is important to establish the normal range of symptoms and arrhythmias in this populaton in order to reduce unnecessary testing and to provide reassurance to women whose symptoms are within normal limits.